# Determine the speed of the shuttle craft

1. May 21, 2009

### fredrick08

1. The problem statement, all variables and given/known data
A spaceship moves away from the earth at a speed v, and fires a shuttle craft in the forward direction at a speed v relative to the ship. The pilot of the shuttle craft forward launches a probe at a speed v relative to the shuttle craft. Detrmine:

a) the speed of the shuttle craft relative to Earth
b) the speed of the probe relative to Earth

3. The attempt at a solution
Im just completely confused with this question, do i have to use Lorentz transformations?? but if so, how do i compute an answer?? plz can someone help, completely lost with this one.

2. May 21, 2009

### CompuChip

You can just use the velocity addition formula I suppose.
Apparently someone else is working on the exact same question in this thread.

3. May 21, 2009

### fredrick08

ok for part a, i can use the LT to get u=2v/(1+v^2/c^2) but how do i do b.??

i can use u'=u from part a, but im sure if this is what i have to do

4. May 21, 2009

### tyco05

I think you are making it harder for yourself than it actually is.